Some Coastal Cities Must Prepare for Tsunamis by 2060, Scientists Warn

"The very modest change in sea level changed the tsunami hazard."

In recent years, we’ve learned that sea level rise will put coastal cities at risk of greater flooding due to storm surges and at risk of flooding without storms. But new research suggests that sea level rise could also increase the danger of tsunami hazards in those cities, even if they were typically immune from the catastrophic waves in the past. One of these cities is Macau, the Las Vegas of Asia, which stands to lose its world-renowned luxury hotels and casinos if climate change continues at its current pace.

In a paper published Wednesday in the journal Science Advances, an international team of scientists presents evidence that even as little as half a meter — about 1.6 feet — of sea level rise by the year 2060 could double the hazard posed to Macau in the event of earthquake-triggered tsunamis. They also found that an increase of a full meter by 2100 could quadruple the tsunami hazard threat. Snce scientists estimate that sea levels will rise anywhere from one to four feet by the end of this century, most of us could very well live to see the scenario predicted in this hazard estimate.

“We commonly hear about sea level rise, and it is surely a huge issue for many coastal cities worldwide. What is rarely studied is the interaction of other sea level extremes like storms, spring tides, and tsunamis,” Adam Switzer, Ph.D., principal investigator at Nanyang Technological University’s Earth Observatory of Singapore and one of the paper’s authors, tells Inverse.

“We wanted to see what sea level would do to tsunami risk in a city that is considered somewhat ‘tsunami safe’.” Hence their focus on Macau, a city-state that has not typically been threatened by tsunamis.

The glittering metropolis of Macau could be seriously threatened by tsunamis in the next few decades.

To do this, the researchers used computer models to simulate how Macau would be affected by the tsunami created by a megathrust earthquake that originated along the Manila Trench in the South China Sea. At current sea levels, they found that even a very strong earthquake of 8.4 magnitude wouldn’t affect Macau very much, which basically confirmed what years of history have shown to be the case: Macau isn’t in danger from tsunamis.

“The real surprise came from how much the very modest change in sea level changed the tsunami hazard,” says Switzer. With a mere half-meter of sea level rise, the hazard doubled. This could be bad news for Asia’s casino capital, but Switzer and his colleagues are interested in more than just Macau.

Based on rates of sea level rise since 1992, half a meter of increase is not a stretch.

“This work is part of a larger program to investigate sea level rise and sea level extremes in Asia that covers sea level rise, storm surges, tsunamis and tidal variations,” he says. “It is well known that Asian coastal cities are among the most vulnerable globally with regard to sea level rise.” He notes that sea level rise does not happen in a vacuum, and on top of sea level rise are all sorts of compounding factors, including tsunamis. As a result of this study, the study’s authors hope that people will pay attention to the threat that sea level rise poses to other Asian cities like Hong Kong.

“This is just one location and expanding this to other coastal cities is an obvious next step,” says Switzer. “We are already collaborating with other groups to do similar work in other tsunami-prone sites worldwide.”